The present invention is directed to a sampling probe for filtering fluid contained in a vessel, and more particularly, to a sampling probe for filtering fluid contained in a vessel, wherein the sampling probe is shaped to be received within an inner chamber of the vessel.
In the bio-processing, pharmaceutical or other related industries, a liquid broth containing cells, fermentation materials, bacteria, cell cultures or other microorganisms may be formed during manufacturing processes. The broth must be periodically checked to monitor the level of certain compositions or byproducts in the broth, such as nutrient waste groups of small molecules, protein concentrations, or other compounds. The broth is typically contained in a large vessel that has a port formed in its top or side, and the port is shaped to receive a probe therethrough for withdrawing a sample of the broth. Typically, the size of the port is set at an industry standard, such as, in one case, a diameter of about 12 mm.
In order to draw a sample from the broth, a generally tube-shaped probe is typically passed through the port in the vessel until one end of the probe is submerged in the broth. A sample of broth is then drawn up through the straw-like probe. A peristaltic or other pump may be used to draw the sample up the probe and out of the vessel. Once the sample is obtained, it is passed through a separate tangential filter element to filter out the cells. In many cases, a second pump is used to draw the broth through the filter element. The filtered fluid may then be analyzed for certain levels of components or byproducts, such as glucose, lactate, amino acids, ammonia, glycerol, etc. The unfiltered portion of the withdrawn broth is returned to the vessel via another dip tube.
There are several drawbacks in the prior art methods for withdrawing a sample. For example, it is desirable to return the unfiltered broth to the vessel. However, in practice, most technicians will not return the unfiltered sample to the broth in order to minimize the possibility of contaminating the broth. When a sample is removed from the vessel, it is felt that returning the sample to the broth risks contaminating the broth. Furthermore, most prior art methods draw a relatively high xe2x80x9chold-upxe2x80x9d volume; that is, a relatively large volume of sampled fluid is removed from the broth. Thus, the relatively high volume withdrawal sample becomes wasted fluid when it is not returned to the broth.
The prior art sampling systems may draw the fluid through a filter element by means of a pump. However, this may cause air to be entrained out of fluid after it is filtered. The bubbles may conglomerate and lock together to block flow through the filter line. Furthermore, precise volumetric measurements are required in analyzing the sample, and entrained air can also thereby cause inaccurate volumetric measurements of the broth. Finally, the prior art designs are vulnerable to contamination and because they require separate pumping and filter apparatuses, and are often bulky and expensive.
Accordingly, there exists a need for a sampling probe which has a low hold-up volume, reduces the entrainment of air, reduces the risk of contamination and is relatively small and inexpensive for easy disposability.
The present invention is a sampling probe for sampling and filtering a portion of material that has a relatively small hold-up volume, reduces the entrainment of air, and is compact and inexpensive. The sampling probe incorporates a pump and a filter into one assembly, and can be accepted into a standard sized port formed in a vessel. Because the probe is inexpensive, it may be disposed of after a single use, which eliminates the possibility of contamination from previous uses. In one embodiment, the invention is a sampling probe for withdrawing and filtering a portion of material from a vessel having an inner chamber containing the material and a port for receiving a probe. The sampling probe comprises a casing having a sample inlet, a pumping chamber having a pump for drawing a portion of the material into the pumping chamber through the sample inlet, and a filter chamber downstream of the pumping chamber. The filter chamber includes a filter which divides the filter chamber into a retentate portion and a filtrate portion, wherein at least part of the withdrawn material passes through the filter into the filtrate portion.
Other objects and advantages of the present invention will become apparent from the following description, the accompanying drawings and the appended claims.